220 VDC Power Supply: Connecting Two 110 VDCs

Yes.

Take care of Polarity.

You will face some problems with the charger.

Yes, though it depends upon isolation. Were both of them to be referenced to Earth, for example, then it wouldn't work unless one was +110VDC and the other -110VDC relative to Earth. In fact, it would prove hazardous to one bank of batteries and anyone present if the connection were made without first having established this isolation, as it would present a short-circuit to one set of batteries.

Would distance between earths be effective?

i have used these inverters and they work well

http://www.powerbright.com/erp3500-12.html

when you play with matching inverters if there is any difference in the inverter you will blow the inverter on a back feed best to get a new inverter

It also depends on the type of charger connected to each battery( Float cum boost charger OR Float and Float cum boost charger ). Alternatively if the 220 V load ( in wattage ) is not high and 110 V charger with battery can support, then it is advisable to go in for a DC/DC convertor operating on 110 V DC from the exisiting 110 V battery & charger ( you can use one of the feeders ) and providing 220 V DC output. As manufacturer of battery chargers, we do get requests for providing 220 V DC output from existing 110 V DC system & most of the cases, the problem is addressed by using DC/DC convertor. Please give charger details as you may face difficulties if one of the charger goes in Boost mode & other one is in Float mode.

Thanks and regards

Ashok Toshniwal, Bangalore - India

I have done it many times.

In my plant we have twelve large combustion turbines and substations each with their own 110VDC( actually 125VDC but that is just academic) .

Pay special attantion to the grounding.

Most large DC battery banks will be isolated from ground with a ground fault monitor.

The monitor will close a contact to produce an alarm on the control system.

I have observed that in the case of leakage where you do not have a "solid' ground , you can generate circulating currents that will be undesirable.

Use a multimeter and and asuming you do have a ground fault monitor make measurements on the battery banks to ensure it is well balanced i.e. you will get +55VDC from the positive terminal of the battery bank to ground and -55VDC from the -ve terminal to ground.

Sometimes you may get a readings which, due to the high impedance of most multimeters, will look like you have a major problem but may just be surface tracking on the sides of the battery bank cells or terminals.

Wipe them clean with some demin water and you should be OK.

Only then should you consider seriesing the supplies.put a couple fuses in the circuit and maybe an ammeter.

IF YOU HAVE A GROUND FAULT ON EACH BATERY BANK , YOU WILL END UP WITH A SHORT CIRCUIT IF YOU SERIES THE TWO BANKS.

It's possible to series your two battery banks if the batteries have the same capacities (i.e. both banks must be the same type and capacity). If you are using this set up for backing up a DC motor generator or DC solid state battery charger for powerplant or substation operations, you probably have a ground detector (to avoid short circuits), therefore it would be important to check your potentials to ground from both banks before trying this (+- 55vdc to gnd on each bank). Also remember that the batteries are only for backup and the DC load is fed by the MG set or the charger, so check your connections first.

Two Inedepedent 110 V DC Batteries can be connected in series to get 220 V DC nothing wrong will happen to either CHargers or Batteries. Big HVDC Systems operates on the same principle.

Ramana.

Dear Friends,

Any suggestion would be greatly appreciated!

I would like to connect my car battery (35amps for Maruthi WagonR) to my 900watts inverter, to get some extra backup, which already runs on 150amps 12volt exide battery. Could anyone suggest any method?